The present invention is directed to methods and devices for protecting a passageway in a body when advancing devices through the passageway. A specific application of the present invention is for treatment of blood vessels although the invention may be used in any part of the body. For example, the present invention is used to protect blood vessels during intravascular procedures for treating aneurysms, arteriovenous malformations, and atherosclerotic disease of vessels. A particular application of the present invention is for atherosclerotic disease of the carotid arteries or saphenous vein grafts. Carotid artery atherosclerotic occlusive disease contributes to hundreds of thousands of strokes annually in the United States. Atherosclerotic disease of the internal carotid artery is particularly problematic since plaque from the internal carotid artery leads directly to the cerebral vasculature.
A conventional method of treating carotid artery occlusive disease is by surgical removal of the plaque (carotid endarterectomy). The carotid artery is opened surgically, the plaque is removed and the carotid artery is then closed. Carotid endarterectomies have demonstrated significant clinical benefit over conservative treatment with medication by reducing strokes over the next five years. Although carotid endarteretomy reduces strokes over a period of time after the procedure, the procedure still has a 6% risk of death or stroke.
Another method of treating carotid artery disease is to use interventional devices such as stents. A problem with treating carotid artery occlusive disease with stents is that the user is wary of dislodging plaque when advancing the stent through the carotid artery. Any plaque which breaks free during introduction of the stent travels directly to the patient""s brain and can cause a stroke or death.
Yet another method of treating carotid artery occlusive disease is to introduce a filter through the carotid artery to trap emboli released during subsequent deployment of a stent or angioplasty balloon. This method suffers the same drawback in that advancement of the filter itself may dislodge plaque. Moreover, exchange of various therapeutic catheters over the filter element result in undesirable movement of the filter with attendant risk of losing filtered emboli or damaging the vessel wall with the filter.
The present invention is directed to improved methods of protecting a body passageway when advancing devices through the body passageway. The present invention is also directed to improved methods of treating atherosclerotic vessels and, in particular, occlusive disease of the internal carotid artery.
In accordance with the objects of the invention, a liner is provided to protect a body passageway during introduction of other devices into the passageway. In a specific application, the methods and devices of the present invention are used to protect blood vessels, such as the internal carotid artery, during intravascular procedures. It is understood that use of the present invention for protection of blood vessels is discussed as an example of how the present invention may be used, however, the invention may be used in any other part of the body without departing from the scope of the invention. The liner is collapsed for introduction into the patient and advanced to a narrowed region of a blood vessel. The liner is passed through a region of the blood vessel in the collapsed condition and an intravascular device, such as a stent or filter, is then introduced into the liner. The liner may be used to protect vessels from any type of problem including atherosclerotic disease, perforation, aneurysm or AVM.
The liner protects the vessel as the intravascular device is passed through the region to prevent the device from dislodging plaque. When the device is a stent, the stent is preferably expanded within the liner to trap the liner between the stent and the vessel. The liner may be expanded by the stent or may be partially or fully expanded before introduction of the stent. The devices and methods of the present invention are particularly useful for treating occlusive disease of the internal carotid artery. The liner may be any suitable material and suitable materials include expanded PTFE, woven dacron, nylon, low durometer silicone, or thin-walled polyethylene.
The liner is preferably mounted to a delivery catheter and is advanced over a guidewire. The liner may have an anchor at a proximal end which is used to open the proximal end of the liner. The anchor may be self-expanding or balloon expandable. Once the proximal end of the liner is opened, the liner can be designed so that blood pressure opens the liner. Alternatively, the liner may open automatically or may be opened with a separate device, the delivery catheter or the stent itself. When treating occlusive disease of the internal carotid artery, the anchor may be positioned completely in the internal carotid artery or may extend from the common carotid artery across the bifurcation of the internal and external carotid arteries and into the internal common carotid. The anchor preferably has an open structure which permits blood flow into the external carotid artery.
The liner may be an elastic liner or may be folded into a collapsed position. The liner may be collapsed in any suitable manner and preferably has a number of folded sections which are wrapped around one another. The folded sections are preferably adhered to one another to hold the liner in the collapsed position. The folded sections may be adhered together by application of heat or with an adhesive or coating. The distal end of the liner may be coated to form a curved surface which covers the ends of the folded sections. Alternatively, the ends of the liner may be scalloped or contoured so that when folded the edge tapers down more cleanly.
The liner may also be designed to evert when expanding. The everting liner reduces sliding between the liner and vessel so that plaque is not dislodged when introducing the liner. An end of the everting liner may be releasably attached to the delivery catheter.
The proximal end of the liner may also be opened with an expandable device, such as a balloon, on the delivery catheter rather than with an anchor attached to the liner. Once the proximal end is open, the stent or other device is advanced through the liner.
In yet another aspect of the invention, the catheter holds the proximal end partially open. The stent or other device is then advanced through the open proximal end. The liner can be released when using a stent or may be removed after use.
These and other features and advantages of the invention will become evident from the following description of the preferred embodiments.
The present invention is also directed to a device for lining a vessel which has an expandable anchor movable from a collapsed shape to an expanded shape. The liner attached to the anchor and extends from an end of the anchor. The liner is held between thin, flexible inner and outer layers which are preferably shrink tubing. The outer layer is retracted to expose and free the liner. The outer layer may also hold the anchor in the collapsed position.
The inner and outer layers preferably have a thickness of 0.0005-0.002 inch. The outer layer stretches over a tapered portion and is preferably flexible enough to stretch over the tapered portion as it passes over the tapered portion. The outer layer has a diameter of no more than 0.055 inch, and more preferably no more than 0.050 inch, when in the collapsed position. A radiopaque coil may also be provided which extends beyond the distal end of the liner and between the inner and outer layers. The inner layer is preferably attached to an inner element and the outer layer is preferably attached to an outer element.